Development and validation of a standardized oxidation assay for the accurate measurement of the ability of different wines to form “de novo” oxidation-related aldehydes

Those previous years, pesticides are often brought to the forefront by media. Questions arose about their toxicity for growers and consumers. Even if a downward trend is underway, the use of pesticides is required to ensure steady quality and quantity of harvests. A large number of active ingredients are authorized but regarding viticulture, mainly insecticides and fungicides are applied, to control pests and diseases and to increase crop yield. Some phytosanitary products, principally fungicides, applied close to the harvest date may frequently be detected in wines.

During wine aging, several complex phenomena of gas transfer take place in barrels due to the wine/oak contact. The efficiency of this gas transfer varies according to oak wood’s intrinsic physical properties. This research aims to better understand oxygen transfer phenomena through dry oak staves and especially through stave gaps, in order to reevaluate the importance of barrel-making on a barrel’s supply of oxygen. Experimentation was based on the development of an innovative permeameter of laboratory scale, for which the principal operating conditions concerning applied pressure, the choice of liquid phase/gas phase, and the grain type of oak are taken into account and investigated. With a specially developed tightening system, the existing pressure at stave gaps in a barrel could be reproduced on a laboratory scale in order to estimate its influence on oxygen transfer efficiency.

The assessment of red wine mouthfeel relies primarily on the sensory description of its tannic properties. This evaluation could be improved by gaining a better understanding of the physicochemical properties of these tannins. Hence, the objectives of the present study were threefold: (1) to gain an insight into the sensory properties of subpopulations of proanthocyanidic tannins of different molecular sizes obtained through several ultrafiltration steps, (2) to quantify the kinetics of haze formation of these proanthocyanidic tannins in a dynamic polyvinylpyrrolidone (PVP) precipitation test, (3) to determine whether a correlation exists between the sensory and the precipitation data.

Oligosaccharides have only recently been characterized in wine, and the information on composition and content is still limited. In wine, these molecules are mainly natural byproducts of the degradation of grape berry cell wall polysaccharides. Wine oligosaccharides present several physicochemical properties, being one relevant factor linked to the astringency perception of wines (1,2). A terroir can be defined as a grouping of homogeneous environmental units based on the typicality of the products obtained. This notion is particularly associated with wine, being the climate and the soil two of the major elements of terroir concept.

Despite the extensive research performed during the last decades, the multifactorial mechanism responsible for the white wine protein haze formation is not fully characterized. Herein, a new model is proposed, which is based on the experimental identification of sulfur dioxide as a major modulating factor inducing wine protein haze upon heating. As opposed to other reducing agents, such as 2-mercaptoethanol, dithiothreitol and tris(2-carboxyethyl)phosphine hydrochloride (TCEP), the addition of SO2 to must/wine upon heating cleaves intraprotein disulfide bonds, hinders thiol-disulfide exchange during protein interactions and can lead to the formation of novel inter/intraprotein disulfide bonds. Those are eventually responsible for wine protein aggregation which follows a nucleation-growth kinetic model as shown by dynamic light scattering [1].